1. Technical Field
The present disclosure regards the field of chemical and electronic industry. In particular, the disclosure regards new carbazole derivatives bearing metallocene alkyl substituents on the benzene rings and their use as basic functional units for computing systems based on the QCA (Quantum Cellular Automata) paradigm.
2. Description of the Related Art
The QCA paradigm was elaborated in the '90s at the University of Notre Dame, Illinois, by C. S. Lent and collaborators (see, C. S. Lent, P. Douglas Tougaw, W. Porod, G. H. Bernstein, Nanotechnology 1993, 4, 49) and represents a transistor-less alternative to current computers, adapted for downscaling size and a power consumption beyond Moore's law.
According to the QCA paradigm, the fundamental computational unit (cell) is an arrangement of four quantum dots at the corners of a square, with possibly a fifth dot at the center. The dots are charged with two electrons with opposite spin, capable of tunneling between dots of the cell but not outside the cell.
The electrons are normally localized along a diagonal of the cell, in order to minimize internal repulsion, and the diagonals thus code the two stable states for binary logic and arithmetic. The choice of the diagonal will depend on the energy of the ground state of the single dots, which in turn depends on the arrangement of the electrons inside the surrounding cells (especially those in the neighborhood). Therefore, electrostatic interaction is the driving force for making the different cells work together: when the charge configuration inside a cell changes, the neighboring cell will consequently change, while the electrons move around the dots of the cell and resettle onto the new minimal energy configuration.
The use of bistable molecules in computing systems based on the QCA paradigm was described in various studies, including J. Jiao, G. J. Long, F. Grandjean, A. M. Beatty, T. P. Fehlner, J. Am. Chem. Soc. 2003, 125, 7522; Y. Lu, C. S. Lent, J. Comput. Elec. 2005, 4, 115; H. Qi, S. Sharma, Z. Li, G. L. Snider, A. O. Orlov, C. S. Lent, T. P. Fehlner, J. Am. Chem. Soc. 2003, 125, 15250; C. S. Lent, B. Isaksen, M. Lieberman, J. Am. Chem. Soc. 2003, 125, 1056.
Tricyclic compounds such as carbazole derivatives can be used as bistable molecules for computing systems based on the QCA paradigm. A carbazole derivative is known to contain a ferrocenyl vinyl substituent, and specifically the compound of the following formula.

Such compound is known from Wang Xu-Chun et al., Transition Metal Chemistry, Vol. 32, No. 5, August 2007, pages 551-557.